Production of oil and gas is a trillion dollar industry. To get oil and gas out of the earth, large costly equipment is used under extreme conditions. For example, reciprocating pumps that generate very high pressures are used for pumping liquids into and out of holes that are miles deep. Such pumps are either pumping against the pressure of fluids trapped beneath millions of tons of rock or taking suction of those fluids, so they must be functional for long periods of time under extreme stress.
One example of a reciprocating pump that routinely develops pressures of several thousand pounds per square inch is a drilling fluid pump. Drilling fluid (also called “drilling mud”) is a dense, viscous substance pumped into an active drilling hole to cool the drilling bit, lubricate the drill stem, support the walls of the wellbore, discourage premature entry of fluids into the wellbore, reveal the presence of oil or gas in a drilling formation, and carry cuttings to the surface where they can be removed. Higher viscosity drilling fluid is able to carry more and heavier cuttings, so additives are frequently used to increase viscosity. Pumping a high viscosity, high density fluid into a highly pressurized wellbore through miles of pipe requires very high pressure.
Reciprocating force delivery devices such as drilling fluid pumps operate by guiding a piston along a cylinder. One end of the cylinder is coupled to a fluid manifold which admits fluid when the piston is retracted. When the piston is advanced the fluid is forced from the manifold under pressure. The piston is generally driven by a rod or rod assembly coupled to a motor.
The cylinder forms a seal with the fluid manifold that must be maintained by urging the cylinder against the fluid manifold. A retention device is used to apply the sealing force to the cylinder. Prior art retention devices rely on rings that must be bolted to the fluid manifold by applying balanced tensile loads to the bolts to avoid unbalanced sealing force resulting in a weak seal. Other prior art retention devices rely on complex hardware with numerous parts to enable use of hydraulic force to balance the load on the seal. In many cases, sealing and seating of prior art devices is aided by hydraulic mechanisms that require hydraulic fluids, use of which may harm local ecosystems. It is also common to use potentially unsafe methods of impulse torquing (i.e. hitting with a sledgehammer) to complete seating and sealing. Moreover, while it is desirable to apply a balanced load to seal the cylinder to the fluid manifold, oil field equipment often must be operated far from available supplies of parts. Equipment having few parts that are easily assembled is generally favored.
Thus, there remains a need for a cylinder retention device for a reciprocating force delivery device that provides a load-balanced seal with minimal parts and easy assembly.